Tomosynthesis is an advanced three-dimensional radiographic imaging technique in which several 2-D images of a patient are taken at different angles and/or planes, and then these images are reconstructed as a 3-D image of the volume of the patient that was imaged. Unlike conventional x-ray imaging techniques, radiographic tomosynthesis provides depth information about an area of interest within an object being imaged, such as a tumor or other anatomy within a patient. Tomosynthesis also enables any number of tomographic slices to be reconstructed from a single scanning sequence of x-ray exposures, without requiring additional x-ray imaging, thereby making tomosynthesis a desirable characterization tool.
The two most common tomosynthesis system architectures comprise either a table configuration (i.e., an x-ray tube located above the patient and a digital x-ray detector located underneath the patient) or a wall-stand configuration (i.e., an x-ray tube located in front of the patient and a digital x-ray detector located behind the patient). The x-ray tube generally sweeps along an arc, circle, ellipse, hypocycloid, line, or any other suitable geometry, to generate a series of projection images on the x-ray detector, and then the series of projected images are reconstructed using a 3-D reconstruction algorithm. Collecting images from a variety of angles in this manner allows depth information to be incorporated into the final image. However, due to the height, size, layout, dimensions, etc., of the imaging room, these images can generally only be acquired over a limited area (i.e., normally angles less than 60°), thereby limiting the slice sensitivity and quality of the acquired image data.
Tomosynthesis is generally accomplished utilizing symmetric acquisition geometry. In other words, the sweep angle above and below the center of the x-ray detector, or on one side of the center line of the x-ray detector and on the opposite side of the center line of the x-ray detector, is generally the same. For example, if the dimensions or other limitations of a room only allow enough space to sweep 20 below the center of the x-ray detector, then existing tomosynthesis systems will only sweep 20° above the center of the x-ray detector too so that symmetrical image acquisition is achieved. Therefore, it is clear that the dimensions or other limitations of a room can significantly limit the total sweep angle that is possible in existing tomosynthesis systems. It would be desirable to have tomosynthesis systems that utilize asymmetric image acquisition geometry so that the dimensions, layout, etc., of a room would not be so limiting on the total possible sweep angle. For example, it would be desirable to be able to asymmetrically sweep 30° above and 20 below the center of the x-ray detector, if that is what the room allows.
Since existing tomosynthesis systems and methods have geometric limitations, it would be desirable to have tomosynthesis systems and methods that lack those geometric restrictions. Additionally, it would be desirable to be able to utilize the improved tomosynthesis systems and methods without having to modify the room layout, dimensions, overhead x-ray tube support, x-ray detector support, etc.